Copy prevention method and apparatus for digital video system

ABSTRACT

A copy prevention method and apparatus for a digital video system is disclosed including the steps of: (a) adding a header area of a header start code and key field to a reproduced bit stream: (b) decrypting and transmitting the bit stream to which the header area is added: (c) detecting a key field of the decrypted and transmitted bit stream and detecting copy prevention information; and (d) encrypting the bit stream according to information detected from stop (c) and recording it an tape.

This is a divisional reissue application of Ser. No. 10/737,672 filedDec. 17, 2003 now U.S. Pat. No. Re. 39,319. This reissue application isrelated to another divisional reissue application filed on Nov. 5, 2004of U.S. Pat. No. 6,347,144, and also related to application Ser. No.10/737,971, filed Dec. 17, 2003.

This isNotice: More than one reissue applications have been filed forthe reissue of U.S. Pat. No. 6,347,144. The reissue applications areapplication Ser. Nos. 10/737,671, 10/737,672 (now U.S. Pat. No. Re.39,319), Ser. No. 11/040,606 (now U.S. Pat. No. Re. 41,074), and Ser.No. 11/040,607 which are all reissues of U.S. Pat. No. 6,347,144; Ser.No. 10/981,797 (the present application), Ser. Nos. 10/737,672,10/909,248 and 10/981,798 which are all divisionals of Ser. No.10/737,672; Ser. No. 12/139,161 which is a continuation of Ser. No.10/909,248; and Ser. Nos. 12/405,011 and 12/405,053 which are bothdivisionals of Ser. No. 10/981,798. U.S. Pat. No. 6,347,144 resultedfrom application Ser. No. 09/497,465, which is a continuation ofapplication Ser. No. 09/053,288, filed Apr. 1, 1998, now U.S. Pat. No.6,028,932, which is a continuation of Ser. No. 08/562,042, filed Nov.22, 1995, now U.S. Pat. No. 5,761,302, issued Jun. 2, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to a copy prevention technology for adigital video system, and more particularly, to a copy prevention methodand apparatus for a digital VCR to which encryption is introduced todisplay a picture only in a VCR internally containing a correspondingencryption code, thereby preventing tape from being copied.

General copy prevention methods for analog VCR are presented in U.S.Pat. Nos. 4,819,098, 4,571,642 and 4,577,216.

First, U.S. Pat. NO. 4,819,098 discloses a method in which aninterference signal is inserted into a video waveform in an automaticgain control circuit (AGC) of a VCR. Here, the inserted signal does notaffect the AGC of its monitor but has the AGC of the VCR record anaccurate level of signal on a video tape.

In U.S. Pat. No. 4,571,642 4,577,216, there is presented a method inwhich a phase noise or other corrected signal is inserted into thechrome chroma burst of a video waveform.

However, all the conventional technologies insert a distributing signalto an analog signal using the difference between a circuit of a monitorand a corresponding circuit of a VCR. Some VCRs may perform copynormally despite of copy prevention. Some monitors cannot display imagesof the original video tape. A conventional copy prevention introduced toan analog VCR system is hard to be applied to digital storage media(DSM).

Specifically, in a satellite receiver or high-definition TV decoder, asshown in FIG. 2, an MPEG bit stream received by a digital VCR isconstructed to transmit a transport header, packetized elementary stream(PEG) (PES) header and audio and video data respectively orsimultaneously.

The PES header contains a PES header flag area of 14 bits which is afield for DSM such as digital VCR, and a PES header field having avariable length. The PES header flag area includes 1-bit copyright (CR)flag, 1-bit original-or-copy (OC) flag, 2-bit PD flag, 1-bit TM flag,and 1-bit AC flag.

The PES header field varies in length, and part thereof is set by the PCPD, TM and AC flags. A PTS/DTS area is not present if the value of thePD flag is “00”. It is 40 bits if the value “10”. If the value is “11”,the area is 80 bits. A DSM trick mode field is not present if the TMflag is “0”. If the flag is “1”, the field is 8 bits. An additional copyinformation field is 8 bits if the AC flag is “1”.

When recording is carried out by the satellite receiver orhigh-definition TV decoder and compressed video data is encoded inencoder 101, it is converted into a packet form in packet processingportion 122 102 as shown in FIG. 1. If the compressed audio data isencoded in audio encoder 103, it is converted into a packet form inpacket processing portion 104.

When the outputs of packet processing portions 102 and 104 aremultiplexed in transmission multiplexer 105, a fixed transmission streamshown in FIG. 2 is output to a digital VCR. In this case, for copyprevention, a public-key encryption is applied which is suggested inU.S. Pat. No. 4,200,770. This solves disadvantages in key management orkey distribution when a conventional block-cipher or stream cipheralgorithm such as data encryption standard (DES) encrypts or decryptsonly with a secret key.

This public-key encryption system has all users U hold unique encryptionalgorithm E^(PK) _(U) and description algorithm D^(PK) _(U). Here,encryption algorithm E^(PK) _(U) for the public-key is opened as apublic-key to key supply portion 107. Decryption algorithm D^(PK) _(U)for secret key is kept in secret. The characteristics of E^(PK) _(U) andD^(PK) _(U) are as follows.

First, with respect to all users U and message m transmitted, D^(PK)_(U)(E^(PK) _(U)(m))=m.

Second, encryption algorithm E^(PK) _(U) and decryption algorithm D^(PK)_(U) do not require complicated calculation.

Third, it is impossible to find D^(PK″) _(U) satisfying D^(PK″) _(U)(E^(PK) _(U)(m))=m from encryption algorithm E^(PK) _(U).

In the encryption system having the above characteristics, as shown inFIG. 3, when user A transmits message m to user B, encrypter 106receiving public-key algorithm E^(PK) _(U) for user B's public-key fromkey supply portion 107 encrypts message m (E^(PK) _(U)(m))=c) andtransmits the result to decrypter 109 via a public channel Here, thepublic channel indicates a channel in which transmitted data is not keptin secret.

Key decrypter 108 receiving the key information from key supply portion107 outputs an algorithm D^(PK) _(B) corresponding to encryptionalgorithm E^(PK) _(B), decrypter 109 decrypts (D^(PK) _(B)(c))=m) theoutput of encrypter 106 with decryption algorithm D^(PK) _(B), and thentransmits to user B. In other words, only user B can decrypt decryptionalgorithm D^(PK) _(B) corresponding to encryption algorithm E^(PK) _(B).

A concept developed from the public-key encryption is presented in U.S.Pat. No. 4,405,829. This public-key encryption system is called RSAsystem. A method in which the RSA public-key encryption is efficientlycalculated via batch processing is presented in U.S. Pat. No. 4,964,164.

However, this public-key encryption is inappropriate for high-velocityencryption. A CA system is intended to present prevent illegal viewviewing. However, there is no method of protecting a program distributedthrough a digital storage medium, such as a digital VCR.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide anillegal copy prevention method and apparatus for a digital video systemin which, in copy tape, with encrypted key information is transmittedand recorded so that a copied tape is reproducible only in a VCR havinga corresponding encrypted key information, thereby prevented copypreventing copying.

To accomplish the object of the present invention, there is provided acopy prevention method for a digital video system comprising the stepsof (a) adding a header area of a header start code and key field to areproduced bit stream; (b) decrypting and transmitting the bit stream towhich the header area is added; (c) detecting a key field of thedecrypted and transmitted bit stream and detecting copy preventioninformation; and (d) encrypting the bit stream according to informationdetected from step (c) and recording it on tape.

For the object of the present invention, there is provided a copyprevention apparatus for a digital video system comprising: areproduction block for adding key information to a reproduced bitstream, and decrypting and transmitting it; and a recording block forsearching key information of the bit stream transmitted from thereproduction block is to extract copy prevention information, andencrypting and recording the bit stream according to the extracted copyprevention information.

The reproduction block comprises: reproduction means for reproducingdata recorded on tape; key insertion means for adding key information tothe bit stream of the reproduction means; and decryption means fordecrypting the output of the key insertion means and transmitting it toa recording-side VCR.

The recording block comprises: key detecting/correcting means fordetecting key information from the transmitted bit stream of areproducing-side VCR: copy prevention information detecting means forsearching the key information detected from the key detecting/correctingmeans to detect copy prevention information; encrypting means forencrypting the bit stream according to the copy prevention informationof the copy prevention information detecting means; and recording meansfor recording the bit stream encrypted in the encrypting means.

The copy prevention information detecting means comprises: a PES headerdetecting portion for detecting a PES header from parallel data outputfrom the key detecting/correcting means; and a copy preventioninformation extractor enabled by a PES header detection signal of thePES header detecting portion to detect an additional copy informationfield.

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS

FIG. 1 is a block diagram of a conventional packet processing apparatus;

FIG. 2 shows an example of a general transmission stream;

FIG. 3 is a block diagram of a conventional public-key encryptionsystem;

FIG. 4 shows connections of systems of the present invention;

FIG. 5 is a block diagram of a copy prevention apparatus for a digitalvideo system of the present invention;

FIG. 6 is a block diagram of the copy prevention information detector ofFIG. 5;

FIG. 7 is a circuit diagram of the PES header detector of FIG. 6;

FIGS. 8A-8F are waveform diagrams of input/output at the respectrespective portions of FIG. 7;

FIG. 9 is a circuit diagram of the copy prevention information extractorof FIG. 4;

FIGS. 10A-10G are waveform diagrams of input/output at the respectiveportions of FIG. 9; and

FIGS. 11A-11D show examples of a bit stream of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a preferred embodiment of the present invention will bedescribed below with reference to the attached drawings.

Referring to FIG. 5, a copy prevention apparatus of the presentinvention comprises a reproducing portion 1 for reproducing datarecorded on tape, a key inserting portion 2 for adding a tape headerstart code and key field at the front end of a bit stream of reproducingportion 1, a decrypting portion 3 for decrypting the output of keyinserting portion 2 and transmitting it as parallel data, a keydetecting/correcting portion 4 for detecting a key field from theparallel data transmitted from decrypting portion 3, a copy preventioninformation detecting portion 5 for detecting a PES header from the keyfield detected and extracting copy prevention information, a copyprevention information correcting portion 6 for correcting the output ofcopy prevention information detecting portion 5 if necessary, anencrypting portion 7 for encrypting the output of copy preventioninformation correcting portion 6, and a recording portion 8 forrecording the output of encrypting portion 7 on tape.

As shown in FIG. 6, copy prevention information detecting portion 6 5comprises a PES header detecting portion 10 for searching the paralleldata in synchronization with a clock clk to detect the PES header, and acopy prevention information extractor 20 enabled by the PES headersignal of PES header detecting portion 10 to detect the copy preventioninformation field.

Referring to FIG. 7, PES header detecting portion 10 comprises first andsecond flipflops 11 and 12 for sequentially delaying the parallel dataaccording to clock elk clk, a packet start code detector 13 forsearching the parallel data and the output of first and second flipflops11 and 12 to detect the packet start code of the PES header, a stream IDdetector 14 for searching the output of second flipflop 12 to detect thestream ID of the PES header, a delay 15 for sequentially delaying theoutput is-pscp of packet start code detector 13 according to clock clk,and a detection signal generator 16 for logically multiplying theoutputs of delay 15 and stream ID detector 14 and outputting a PESheader detection signal is-PES-header.

As shown in FIG. 9, copy prevention information extractor 20 comprises aD-flipflop 21 for holding the parallel data output from PES headerdetector 10, a D-flipflop 22 for holding PES header detection signalis-PES-header of PES header detector 10, a D-flipflop 23 cleared by theoutput of D-flipflop 22 and holding voltage (+5V) by a CR signal of theoutput of D-flipflop 21 and outputting a signal LCR, a D-flipflop 24cleared by the output of D-flipflop 22 and holding voltage (+5V) by anOC signal of the output of D-flipflop 21 and outputting a signal LORLOC, a copy prevention information position operator 25 for searchingthe parallel data of PES header detector 10 and calculating the positionof an additional copy information field, a counter 26 for counting theoutput of copy information position operator 25, and a D-flipflop 27 forholding the additional copy information field of the output ofD-flipflop 21.

The operation and effect of the present invention will be explainedbelow. Generally, in case of reproducing or copy recording data on tapatape, connections between systems are made as shown in FIG. 4.

With those connections, an MPEG bit stream reproduced from VCR A isinput to a satellite receiver or high-definition TV so that it cannot berecognized whether the stream is displayed on a screen or input to VCR Band recorded on another video tape.

For this reason, according to the present invention, in case that thebit stream reproduced from VCR A is copied from VCR B, information oncopy prevention is transmitted to VCR B from VCR A. VCR B analyzes thisinformation which is recorded with the bit stream.

Here, the insertion position of the copy prevention informationcontained in a GA bit stream is very limited because it must not affectdecoding of the decoder of the satellite receiver or high-definition TVso that an image is displayed normally on a monitor. The copy preventioninformation may be inserted into the front end of the MPEG bit stream orinside the PES header.

When the MPEG bit stream is decoded in units or of group of picture(GOP), the respective GOPs are classified by their cop GOP start codes.This is useful in transmitting initialization data to a recording-sideVCR because decoding is never affected even when a slight amount of datais added to the front end of the MPEG bit stream.

The case of inserting the copy prevention information into the PESheader is useful in repeated transmission of information because copyprevention of a recording medium such as DSM is decided using CR and OCflaps of the PES header and additional copy information field. In thiscase, there are a variety of copy preventing methods.

First, when a mode of “No Copy” is detected from the additional copyinformation field of the PES header, VCR B is not able to enter itsrecording mode.

Second, when a mode of “Copy Permitted” is detected in order toimplement a copy prevention such as DAT mode, VCR B records but “NoCopy” mode is recorded in the additional copy information field tointerrupt recopying from a copying tape. This means that a secondarysource tape can be made, but a third source tape cannot.

Third, for “Back-up Copy”, tape B copied from VCR B is reproduciblenormally only is VCR A. According to this method, reproducing-side VCR Aencrypts the bit stream with its own inherent key and records it on tapeso that only reproducing-side VCR A decrypts the MPEG bit streamrecording on the tape. For every VCR set, a unique key is provided,encrypted by VCR's key and recorded on tape B. However, the VCR set foerecording tape B is VCR B and tape B is encrypted by VCR A's key so thatVCR A's key needs to be transmitted to VCR B with GA bit stream.

Accordingly, when the key information of VCR A is transmitted as aheader in advance prior to the bit stream in the “Back-up Copy”, it isrecorded at the front end of tape B, which satisfies the insertionposition of the copy prevention information mentioned before.

Here, as shown in FIG. 2, the position of the additional copyinformation field is varied within the PES header according to whetherpresentation time stamp (PTS)/Decoding time stamp (DTS) and DSM trickmode field are present or not. This varied position must be compensated.Here, information transmitted through the additional copy information isa copy prevention method to be performed by recording-side VCR B.

In case of recording the bit stream shown in FIG. 11A in the method of“Back-up Copy”, the formal of the bit stream recorded on tape isdetermined as shown in FIG. 11B.

Here, a header area added to the front of the MPEG bit stream is formedwith a tape header start code, that is, the header identifier code, anda key field for storing key information. In case of encrypting the MPEGbit stream in units of GOP, encryption blocks are classified by thepacket start code prefix and stream ID of the PES header. The encryptionblock is a basic unit of encryption and can change whether encryption isperformed in units of the encryption block, and encryption algorithm andkey selection. Here, the encryption blocks must not be encrypted untilthe additional copy information field of the PES header. Encryption isperformed until the end of the encryption block after the additionalcopy information field. The first ‘transmission header’ is notencrypted.

The operation of performing the “back-up Copy” mode by adding the headerwill be described below.

First, in copying, when recording data of tape A is encrypted,reproducing-side VCR A decrypts it using the key information of the keyfield so is to make message m. Its key information is added to theheader and transmitted in the formal of FIG. 11C.

Recording-side VCR B records the key information transmitted fromreproducing-side VCR A on the header of copying tape B and then recordsthe encrypted bit stream. Here, when the key information is transmittedfrom reproducing side to recording side, for security, a public-keyencryption may be employed to the system because the information may beexposed to a pirate.

Such public-key encryption system ensures the secret of data even thoughthe public-key is exposed but cannot be processed in real-time due to agreat amount of calculation. Therefore, this system is not improper whenthe MPEG bit stream is encrypted directly. The “Back-up Copy” can beimplemented when the MPEG bit stream is encrypted using a block-cipheralgorithm or stream-cipher algorithm such as DES and a key used isencrypted in the public-key encryption.

In this case, every VCR u incorporates encryption algorithm E^(PK) _(U)corresponding to the public-key and decryption algorithm D^(PK) _(U)corresponding to the secret key. Encryption algorithm E^(PK) _(U) takesa power key of VCR u, and decryption algorithm D^(PK) _(U) an internalkey of VCR u.

Here, the internal key may be opened to the public. Reproducing-side VCRA transmits the internal key on the key field of the header becauseanother VCR encrypts using the internal key. Recording-side VCR Brandomly selects a key Y used in the block-cipher algorithm such as DESand encrypts it with the public-key encryption system using an externalkey E_(PK) _(A). The result is recorded on the key field of copying tapeB.

Sequentially, the data is divided into encryption blocks and encryptedand recorded in the block-cipher algorithm using key Y. In this method,the bit stream of FIG. 11D is recorded on copying tape B.

When copying tape B is reproduced in reproducing-side VCR A, key Y canbe restored by decryption D^(PK) _(A)[E^(PK) _(A)(Y)] in which data isdecrypted properly. In other VCRs, key Y cannot be found, which disablesthe decryption of the bit stream.

AsAn embodiment of the present invention, shown in FIG. 5, forperforming such an operation will be described below.

When playback starts for tape copying, reproducing portion 1 detectsdata recorded on tape as shown in FIG. 11A, and amplifies it by apredetermined level. As shown in FIG. 11B, key inserting portion 2 addsa header having a tape header start code and key field in the GA bitstream of reproducing portion 1 shown in FIG. 11A. Copy preventioninformation is loaded on the additional copy information field of thePES header to form a format shown in FIG. 11C. Here, decrypting portion3 decrypts the bit stream formed in key inserting portion 2 andtransmits it as parallel data to the recording-side VCR via aninterface.

When the bit stream of FIG. 11C is transmitted to the recording-side VCRvia the interface, key detecting/correcting portion 4 detects the keyfield added to the bit stream and corrects the key field if necessary.

Copying prevention information detecting portion 5 searches the PESheader area to detect the additional copy information field. Here,though a slight amount of information is recorded in the additional copyinformation field, redundancy is provided in several areas of the bitstream to increase reliability of information transmitted.

Copy prevention information detecting portion 5 extracts the value of ACflag from the PES header flag in order to calculate the position of theadditional copy information field because it varies within the PESheader. Here, when copy prevention information correcting portion 6corrects the output of copy prevention information detecting portion 5,encrypting portion 7 performs encryption using the block-cipheralgorithm such as DES. Here, copy prevention information correctingportion 6 performs correction while the input data is stored in a RAM.Accordingly, encrypting portion 7 records the encrypted bit stream ontape in recording portion 8. Because the key information of thereproducing-side VCR is added on the copying tape, only a VCR havingthis key information can reproduce tape normally.

As shown in FIG. 6, in copy prevention information detecting portion 5,PES header detecting portion 10 searches the output of keydetecting/correcting portion 4 and outputs a header detection signalis-PES-header. After header detection signal is-PES-header is input,copy prevention information extractor 20 detects the additional copyinformation field and OC and CR flags.

PES header detector 10 for detecting the PES header is formed as shownin FIG. 7. When bit stream data_in is input as shown in FIG. 8A, firstflipflop 11 synchronized to clock clk is delayed for a predeterminedtime to output the bit stream delayed as shown in FIG. 8B. Secondflipflop 12 delays the output of first flipflop 11 by are predeterminedtime and outputs the bit stream delayed as shown in FIG. 8C.

Here, packet start code detecting portion 13 searches the bit streamshown in FIG. 8A and the output of first and second flipflops 11 and 12shown in FIGS. 8B and 8C in order to detect the packet start code of thePES header. When detection signal is-pscp is output as shown in FIG. 8D,delay 15 in which flipflops are coupled at multi-stages delays itsequentially according to clock clk.

Meanwhile, stream ID code detector 14 searches the output of secondflipflop 12 and detects the stream ID area of the PES header. Then,detection signal is-sid shown in FIG. 8E is output to detection signalgenerator 16. Detection signal generator 16 logically multiplies theoutputs of delay 15 and stream ID code detector 14, and the flipflopshold the output of the AND gate according to clock clk so that PESheader detection signal is-PES-header is output to copy preventioninformation extractor 20 as shown in FIG. 8P 8F.

Here, copy prevention information extractor 20 for detecting the copyprevention information is formed as shown in FIG. 9. When the paralleldata output from PES header detector 10 and shown in FIG. 10A is heldand output as shown in FIG. 10B, D-flipflop 22 synchronized to PESheader detection signal is-PES-header of PES header detector 10 shown inFIG. 8F holds voltage +5V so that a HIGH signal is output to the clearports of D-flipflops 23, 24 and 27 to release the clear states.

D-flipflop 23 is synchronized to the CR flag or the output of D-flipflop21 shown in FIG. 10B to hold voltage Vcc so that a HIGH signal LCR isoutput as shown in FIG. 10C. D-flipflop 24 is synchronized to the OCflag of the output of D-flipflop 21 to hold voltage Vcc so that a HIGHsignal LOC is output as shown in FIG. 10D.

Copy prevention position detector 25 searches the PD, TM and AC flags ofthe parallel data of PES header detector 10 shown in FIG. 10A tocalculate the position of the additional copy information field, whichis output to counter 26 as shown in FIG. 10E. Counter 26 receiving the4-bit value performs counting so that a HIGH signal is output as shownin FIG. 10F at a predetermined counting value.

D-flipflop 27 synchronized to HIGH output rco of counter 26 holds theadditional copy information field from the parallel data of D-flipflop21 shown in FIG. 10B. The field is output as shown in FIG. 10C.

As described above, in the copy prevention method and apparatus for adigital video system of the present invention, a key information isrecorded with a bit stream so that a VCR having the key informationreproduces tape normally, thereby preventing illegal copy of tape. Inaddition, for key information transmission, the public-key encryption isintroduced to disable a pirate to release the copy prevention,increasing reliability of copy prevention.

1. A copy prevention method for a digital video system comprising thesteps of: (a) receiving a digital data stream reproduced from a digitalmedium; (b) detecting an encryption key, which is a portion of saidreceived digital data stream; (c) decrypting said encryption key usingkey information; (d) decrypting said received digital data stream basedon said decrypted encryption key; and (e) transmitting said decrypteddigital data stream to at least one of a monitor and a digital recorder.2. A copy prevention method for a digital video system as claimed inclaim 1, wherein said key information is predetermined by said digitalvideo system.
 3. A copy prevention method for a digital video system asclaimed in claim 1, wherein said decrypting step (d) is operated inunits of predetermined block of said received digital data stream.
 4. Acopy prevention apparatus for a digital video system comprising:receiving means for receiving a digital data stream reproduced from adigital medium; a key detector to detect an encryption key, which is aportion of said received digital data stream; a decryption unit todecrypt said encryption key using key information and to decrypt saidreceived digital data stream based on said decrypted encryption key; anda controller to control transmission of said decrypted digital datastream to at least one of a monitor and a digital recorder.
 5. A copyprevention apparatus for a digital video system as claimed in claim 4,wherein said key information is predetermined by said digital videosystem.
 6. A copy prevention apparatus for a digital video system asclaimed in claim 4, wherein said decryption unit is operated in units ofpredetermined block of said received digital data stream.
 7. A copyprevention method for a digital video system comprising the steps of:(a) receiving a digital data stream reproduced from a digital medium;(b) detecting an encryption key, which is a portion of said receiveddigital data stream; (c) decrypting said encryption key using keyinformation; (d) decrypting said received digital data stream based onsaid decrypted encryption key.
 8. A copy prevention method for a digitalvideo system as claimed in claim 7, wherein said key information ispredetermined by said digital video system.
 9. A copy prevention methodfor a digital video system as claimed in claim 7, wherein saiddecrypting step (d) is operated in units of predetermined block of saidreceived digital data stream.
 10. A copy prevention apparatus for adigital video system comprising: receiving means for receiving a digitaldata stream reproduced from a digital medium; a key detector to detectan encryption key, which is a portion of said received digital datastream; a decryption unit to decrypt said encryption key using keyinformation and to decrypt said received digital data stream based onsaid decrypted encryption key.
 11. A copy prevention apparatus for adigital video system as claimed in claim 10, wherein said keyinformation is predetermined by said digital video system.
 12. A copyprevention apparatus for a digital video system as claimed in claim 10,wherein said decryption unit is operated in units of predetermined blockof said received digital data stream.
 13. A copy prevention method for adigital video system comprising the steps of: (a) receiving a digitaldata stream reproduced from a digital medium; (b) detecting anencryption key, which is a portion of said received digital data stream;(c) decrypting said encryption key using predetermined key information;(d) decrypting said received digital data stream based on said decryptedencryption key.
 14. A copy prevention method for a digital video systemas claimed in claim 13, wherein said decrypting step (d) is operated inunits of predetermined block of said received digital data stream.
 15. Acopy prevention apparatus for a digital video system comprising:receiving means for receiving a digital data stream reproduced from adigital medium; a key detector to detect an encryption key, which is aportion of said received digital data stream; a decryption unit todecrypt said encryption key using predetermined key information and todecrypt said received digital data stream based on said decryptedencryption key.
 16. A copy prevention apparatus for a digital videosystem as claimed in claim 15, wherein said decrypting unit is operatedin units of predetermined block of said received digital data stream.17. A copy prevention method for a digital data system, comprising thesteps of: (a) receiving first key information; (b) encrypting second keyinformation using said first key information; (c) encrypting digitaldata streams using said second key information; and (d) recording atleast said encrypted second key information and said encrypted digitaldata streams on a digital medium.
 18. The method of claim 17, whereinsaid (b) randomly selects said second key information.
 19. The method ofclaim 17, wherein said step (c) encrypts said digital data streams inblocks.
 20. A copy prevention apparatus for a digital data system,comprising the steps of: an encryption unit receiving first keyinformation, encrypting second key information using said first keyinformation, and encrypting digital data streams using said second keyinformation; and a controller controlling recording of at least saidencrypted second key information and said encrypted digital data streamson a digital medium.
 21. The apparatus of claim 20, wherein saidencryption unit randomly selects said second key information.
 22. Theapparatus of claim 20, wherein said encryption unit encrypts saiddigital data streams in blocks.
 23. A recording medium having a datastructure for controlling operation of copy prevention function in adigital data processing device, comprising: a digital data area storingdigital data encrypted using first key information; and a keyinformation area storing said first key information encrypted usingsecond key information, said first key information operativelycontrolling the decryption of said encrypted digital data in a digitaldata process device.
 24. A copy prevention method for a digital datasystem, comprising: receiving first key information, said first keyinformation for encrypting digital data; encrypting said first keyinformation using second information; and transferring said encryptedfirst key information.
 25. The method of claim 24, wherein saidencrypting step public key encrypts said second key information.
 26. Themethod of claim 24, wherein said transferring step records saidencrypted first key information on a digital medium.
 27. The method ofclaim 24, wherein said transferring step transmits said encrypted firstkey information.
 28. A copy prevention apparatus for a digital datasystem, comprising: an encryption unit receiving first key information,said first key information for encrypting digital data, and encryptingsaid first key information using second key information; and acontroller controlling a transfer of said encrypted first keyinformation.
 29. The apparatus of claim 28, wherein said encryption unitpublic key encrypts said first key information.
 30. The apparatus ofclaim 28, wherein said controller controls recording said encryptedfirst key information on a digital medium.
 31. The apparatus of claim28, wherein said controller controls transmitting said encrypted firstkey information.
 32. A content protection method for a digital datasystem including a controller and an encryption device, the methodcomprising: receiving first key information by the encryption devicewithin the digital data system, the first key information for encryptingdigital content, the digital content including one or more datasegments, the one or more data segments including a header portion and adata portion, wherein at least the data portion is encrypted using thefirst key information and the header portion includes classificationinformation to classify the data portion; encrypting, via the controllercontrolling the encryption device, the first key information usingsecond key information that is different than the first key information;and transferring the encrypted first key information with thecontroller.
 33. The method of claim 32, wherein the second keyinformation is a public key, such that said encrypting step encrypts thefirst key information using the public key.
 34. The method of claim 32,wherein said transferring step includes recording the encrypted firstkey information on a digital storage medium.
 35. The method of claim 32,wherein said transferring step also transmits the encrypted digitalcontent.
 36. An apparatus for content protection, comprising: anencryption device programmed to receive first key information, the firstkey information for encrypting digital data, and programmed to encryptthe first key information using second key information that is differentthan the first key information, wherein the digital data includes one ormore data segments, the one or more data segments including a headerportion and a data portion, wherein at least the data portion isencrypted using the first key information and the header portion is notencrypted and the header portion includes classification information toclassify the data portion; and a controller, coupled to the encryptionunit, and programmed to control the encryption operation and control atransfer of the encrypted first key information.
 37. The apparatus ofclaim 36, wherein the second key information is a public key, such thatsaid encryption device is programmed to encrypt the first keyinformation using the public key.
 38. The apparatus of claim 36, whereinsaid controller is programmed to control recording of the encryptedfirst key information and encrypted digital data on a digital storagemedium.
 39. The apparatus of claim 36, wherein said controller is alsoprogrammed to control a transmitting of the encrypted digital data. 40.A content protection method within a digital data system including acontroller and a generating device, the method comprising: generating,via the controller controlling the generating device, protected digitalcontent, the protected digital content including one or more datasegments, the one or more data segments including a header portion and adata portion, wherein at least the data portion is protected and theheader portion includes classification information to classify theprotected digital content; and transmitting, via the controller, theprotected digital content and first key information used to generate theprotected digital content, wherein the first key information is requiredto process the protected digital content in a receiving part and isencrypted using second key information different than the first keyinformation.
 41. The method of claim 40, further comprising: encryptingthe first key information using the second key information prior to saidtransmitting step.
 42. The method of claim 41, wherein the second keyinformation is a public key, such that the first key information isencrypted using the public key.
 43. The method of claim 40, wherein thegenerating step includes encrypting the digital content by ablock-cipher algorithm or a stream-cipher algorithm.
 44. A contentprotection method for a digital data system including a controller, arecording device and an encryption device, the method comprising:receiving first key information by the encryption device within thedigital data system, the first key information for encrypting digitaldata, the digital data including a header portion and a data portion;encrypting, via the controller controlling the encryption device, thefirst key information using second information; encrypting, via thecontroller controlling the encryption device, the digital data using thefirst key information, wherein only the data portion is encrypted; andrecording, via the controller controlling the recording device, theencrypted first key information and the encrypted digital data on adigital medium, wherein the header portion includes classificationinformation to classify the encrypted data portion on a digital medium.45. The method of claim 44, wherein the second information is a publickey, such that the first key information is encrypted using the publickey.
 46. The method of claim 44, wherein the header portion and the dataportion comprise a packet.
 47. The method of claim 44, wherein the firstkey information is randomly generated.
 48. A content protection methodfor a digital data system including a controller, a receiving circuitand a decryptor, the method comprising: (a) receiving encrypted digitalcontent and encrypted first key information by the receiving circuitwithin the digital data system, the first key information beingpreviously used for encrypting the digital content, the digital contentincluding a header portion and a data portion, wherein only the dataportion is encrypted; (b) decrypting, via the controller controlling thedecryptor, the first key information using second information; and (c)decrypting, via the controller controlling the decryptor, the encrypteddigital content using the decrypted first key information, wherein theheader portion includes classification information to classify thedigital content, and the step (a) includes classifying the digitalcontent based on the classification information by the controller. 49.The method of claim 48, wherein the second information is a public keysuch that the first key information is decrypted by the public key. 50.The method of claim 48, wherein said step (c) decrypts the encrypteddigital content only when the first key information is normallydecrypted in step (b).
 51. A content protection method within a digitaldata system for content protection including a controller and areceiving circuit, the method comprising: receiving protected digitalcontent and key information which is required to process the protecteddigital content by the receiving circuit, wherein the protected digitalcontent includes one or more data segments, the one or more datasegments including a header portion and a data portion, wherein at leasta portion of the header portion is non-protected; and processing, viathe controller, the protected digital content, based on the received keyinformation, wherein the header portion includes classificationinformation to classify the digital content, and the receiving stepincludes classifying the digital content based on the classificationinformation by the controller.
 52. The method of claim 51, wherein thereceived key information is encrypted, and wherein the processing stepincludes processing the encrypted key information by the processor. 53.The method of claim 52, wherein the protected digital content isprocessed only when the encrypted key information is normally decrypted.54. The method of claim 53, wherein the encrypted key information isdecrypted using second key information.
 55. An apparatus for contentprotection, comprising: a receiving device to receive encrypted digitalcontent and key information, wherein the encrypted digital contentincludes one or more data segments, the one or more data segmentsincluding a header portion and a data portion, wherein at least aportion of the header portion is non-encrypted; a key detecting deviceto detect the key information; and a controller to control a decryptionprocess of the digital content based on the detected key information,wherein the header portion includes classification information toclassify the digital content, and the controller is to classify thedigital content based on the classification information.
 56. Theapparatus of claim 55, wherein the key information is first keyinformation, and wherein said key detecting device is to decrypt thefirst key information using second key information.
 57. The apparatus ofclaim 56, wherein said controller is to decrypt the data portion of eachdata segment using the decrypted first key information.
 58. Theapparatus of claim 55, wherein said controller is to decrypt the dataportion of each data unit using the detected first key information. 59.The apparatus of claim 55, wherein the first key information wasencrypted and predetermined by a digital data system.
 60. An apparatusfor content protection, comprising: a generating device to generateprotected digital content, the protected digital content including oneor more data segments, the one or more data segments including a headerportion and a data portion, wherein at least the data portion isprotected and the header portion includes classification information toclassify the protected digital content; and a controller to transmit theprotected digital content and first key information used to generate theprotected digital content, wherein the first key information is requiredto process the protected digital content in a receiving part and isencrypted using second key information different than the first keyinformation.
 61. The apparatus of claim 60, further comprising: anencryption device to encrypt the first key information using the secondkey information prior to said transmission.
 62. The apparatus of claim61, wherein the second key information is a public key.
 63. Theapparatus of claim 61, wherein the controller is to control theencryption device to protect the digital content by a block-cipheralgorithm or a stream-cipher algorithm.
 64. An apparatus for contentprotection, comprising: a receiving device to receive first keyinformation, the first key information for encrypting digital data, thedigital data including a header portion and a data portion; anencryption device to encrypt the first key information using secondinformation, and encrypt the digital data using the first keyinformation, wherein only the data portion is encrypted; a recordingdevice to record the encrypted first key information and the encrypteddigital data on a digital medium; and a controller, coupled to theencryption device and the recording device, to control the encryptionoperation and the recording operation, wherein the header portionincludes classification information to classify the encrypted dataportion, and wherein the controller is to classify the encrypted dataportion based on the classification information.
 65. The apparatus ofclaim 64, wherein the second information is a public key, and theencryption device is to encrypt the first key information using thepublic key.
 66. The apparatus of claim 64, wherein the header portionand the data portion comprise a packet.
 67. The apparatus of claim 64,wherein the first key information is randomly generated.
 68. Anapparatus for content protection, comprising: a receiving device toreceive encrypted digital content and encrypted first key information,the first key information being previously used for encrypting thedigital content, the digital content including a header portion and adata portion, wherein only the data portion is encrypted; a decryptiondevice to decrypt the first key information using second information anddecrypt the encrypted digital content using the decrypted first keyinformation; and a controller, coupled to the receiving unit and thedecryption unit, to control the decryption operation, wherein the headerportion includes classification information to classify the digitalcontent, and wherein the controller is to classify the digital contentbased on the classification information received from the receivingdevice.
 69. The apparatus of claim 68, wherein the second information isa public key.
 70. The apparatus of claim 68, wherein said controller isto control the decryption device to decrypt the encrypted digitalcontent only when the first key information is normally decrypted. 71.An apparatus for content protection, comprising: a receiving device toreceive protected digital content and key information required toprocess the protected digital content, wherein the protected digitalcontent includes one or more data segments, the one or more datasegments including a header portion and a data portion, wherein at leastthe header portion is non-protected; a processor to process theprotected digital content, using the received key information; and acontroller, coupled to the receiving device and the processor, tocontrol the processing of the protected digital content, wherein theheader portion includes classification information to classify thedigital content, and wherein the controller is to classify the digitalcontent based on the classification information received from thereceiving unit.
 72. The apparatus of claim 71, wherein the received keyinformation is an encrypted key information.
 73. The apparatus of claim72, wherein the controller is to control the processor to process theprotected digital content only when the encrypted key information isnormally decrypted.